Vacuum pump



FIG. 1 is a front, top and right side perspective view showing my design;

FIG. 2 is a front, top and left side perspective view of the design;

FIG. 3 is a top plan view of the design;

FIG. 4 is left side elevational view of the design;

FIG. 5 is a front elevational view of the design;

FIG. 6 is a rear elevational view of the design;

FIG. 7 is a right side elevational view of the design; and,

FIG. 8 is a bottom plan view of the design. 

The ornamental design for a vacuum pump, as shown and described. 